1. Field of the Invention
This invention relates to a fetal electrode apparatus suitable for attachment to a fetus for prenatal examination and monitoring. More particularly, the invention relates to an improved bipolar electrode instrument adapted to be inserted through the vagina and cervix of a woman in labor and secured to a fetus for monitoring fetal heart rate.
2. Description of the Prior Art
During labor it is desirable to monitor continuously fetal physiological signals such as heart rate, pH and the like so as to be aware of the physical condition of the fetus. If the fetus is in distress, the baby can be delivered immediately by a caesarian section. Devices attached external to the mother's body have proven inadequate for monitoring of the fetus because they cannot distinguish clearly the fetal heart rate from that of the mother.
Various other devices have been developed for attachment directly to the fetus. For example, a forcep type electrode device has been used to obtain fetal heart rate. The forcep electrode device usually has pincher electrode clips secured to a plug which is placed at the end of a guide tube. The forcep electrode device is inserted through the passages of a woman in labor by the guide tube, and the clips are squeezed onto the fetal scalp. The guide tube is removed and the clips are connected to monitoring equipment by insulated wires. Disadvantageously, the clips are very brittle and are often cracked or damaged during application. The clips also are not rigidly positioned on the fetal scalp and can pivot about an axis defined by their points of fixation. Such cracking and pivoting of the electrode create electrical noise which interferes with fetal monitoring. Additionally, removal of the clips from the fetus often causes excessive trauma and injury. Upon removal of the clips, the fetal scalp may bleed excessively and the newborn would be susceptible to infections.
In another prior art apparatus, a spiral fetal electrode device has been used to obtain fetal heart rate readings. The device has one or two helical coils attached to a plug which in turn is mounted on the end of a flexible drive tube. An outer insertion tube slides around the drive tube. After inserting the spiral electrode device through the woman's passages and contacting the fetus, the coils are screwed into the fetal scalp by rotating the drive tube within the insertion tube. While inserting the spiral electrode device and rotating same onto the fetal scalp, the helical coils sometimes scrape the mother's tissues or become connected to the mother rather than to the baby. Consequently, the mother's tissues may be damaged or the mother's heartbeat may be read on the monitoring device rather than that of the baby. Additionally, the fragile helical coils occasionally break while being embedded within the fetal scalp. Furthermore, if the spiral fetal electrode device is not removed by carefully counter rotating the helical coils from the fetal scalp, significant trauma and injury can result. By the ripping of the fetal scalp due to improper removal of the spiral electrode, the fetus may sustain a serious scalp wound with significant bleeding and the newborn may become susceptible to infection.